I've used the Karachi Outpost (http://www.crumpler.com …Code=EN&SKU=KOT001-X00150) from Crumpler for 18 months now and it is great. I don't have the largest amount of camera gear but I can fit it all in easily with my 15inch Macbook Pro, jacket, headphones, food and water bottle. Once the straps wore in, it is the most comfortable backpack I've ever used to date. The other big plus, and the reason why I bought this bag, is that you can easily remove the camera compartment and/or the laptop compartment to have a large regular backpack. The side pockets are very well designed as you can access the pockets without taken the bag off (I can get things in and out my side pockets when I'm riding my bike).
There are two little downsides to this bag. One, to get your camera out you need to take the bag off and open it up – the zip is positioned behind your back. At first it was little annoying, but once I figured out how to configure my camera position inside the bag and it was much quicker to pull out when needed. The good point of the zip position is that your camera gear is very secure, which is nice when travelling. And secondly, the bag is not waterproof, it is only water resistant. That said, for your camera gear to get wet, it would require a heavy soaking to get through all the lays of fabric and foam to reach your camera. FYI, I've been stuck in heavy rain for 20 minutes with this bag and my camera was bone dry. I now just keep a little rain cover in one of the side pockets for less than ideal forecasts.
Hope this helps